devcontainer-bake.hcl

// This file prepares only basic target configurations, handling the default base_contexts and output.
// All other config for a target must be overridden by accompanying bake files.
// It also configures a default group with each target listed.

variable "DEVCONTAINER_CACHE_FROMS" {
  default = ""
}
variable "DEVCONTAINER_CACHE_TOS" {
  default = ""
}
variable "DEVCONTAINER_OUTPUTS" {
  default = ""
}

target "layer" {
  name = "${layer.name}"
  matrix = {
    layer = [
      for index, input_layer in devcontainer_layers: {
        name = input_layer,
        index = index
      }
    ]
  }

  // Apply the contexts from options and context
  contexts = { // Establish default base_context from layer order
    base_context = (
      // A default base_context can be inferred only for the second layer and later
      layer.index >= 1
      ? "target:${element(devcontainer_layers, layer.index - 1)}"
      : "no_base_context_provided"
    )
  }

  // Apply cache args from the devcontainer context
  cache-from = [
    for cache_from in split(" ", trimspace("${DEVCONTAINER_CACHE_FROMS}")):
    "${cache_from}-${layer.name}"
  ]
  cache-to = [
    for cache_to in split(" ", trimspace("${DEVCONTAINER_CACHE_TOS}")):
    "${cache_to}-${layer.name}"
  ]

  // Apply the default output to the final layer
  output = (
    layer.index == length(devcontainer_layers) - 1
    ? split(" ", trimspace("${DEVCONTAINER_OUTPUTS}"))
    : null
  )
}

group "default" {
  // Target the last layer as default
  targets = [devcontainer_layers[length(devcontainer_layers) - 1]]
}